编写一Java应用程序，计算圆的面积，当从键盘输入的半径不是double型数值时，产生异常提示：“您输入的不是数值，请从新输入”。（自行测试输入一字符（串）产生的结果-Write a Java application, calculate the area of the circle, when the input　the keyboard is not the radius of the double type, it is a reminder:　your input is not numerical, please　the new input . (self test the result of a character string (string).